Liquid crystal polymers

ABSTRACT

A novel LCP material based on fumarate and maleate di-esters is disclosed having general formula (I); R 1  and R 2  may may not be the same but have general structure (II); (a)=(b), (c), (d); p=2 to 14; q=0 or 1; r=1 or 2; s=1 or 2; X═O, CO 2 , O 2  C, CH 2  ; Y═C 2  H 4 , O, CO 2 , O 2  C; Z═CN, halogen, R, CO 2  R, OR, O 2  CR, wherein R=chiral or achiral.

This application is a 371 of PCT/GB93/01018 filed May 19, 1993.

This invention concerns novel liquid crystal polymer (LCP) materials andmethod for preparing same.

BACKGROUND OF THE INVENTION

LCP's are known and are used in the electro-optical device industry, forexample, in optical storage devices, in non-linear optical devices andin pyroelectric devices, see for example, GB 2146787 A and MakromolChem, 186 2639-2647, 1985.

One known type of LCP consists of a polymeric backbone to which areattached pendant side chains which have a chemical structure than ismesogenic, ie. that induces liquid crystalline character, these beingknown as side chain liquid crystal polymers. Work in this field hasidentified a large number of side chain structures which are suitable,see for example GB 2146787 A. For some purposes it is desirable that theLCP shows a smectic C (Sc) or chiral smectic C (Sc*) liquid crystalphase, and a particularly preferred side chain for acheiving this is onewhich contains a laterally fluorinated biphenyl or terphenyl system.

Liquid crystal polyacrylates are known, Polymer Communications, 24,364-365, 1988, having a polyacrylate backbone, eg. polymethacrylate,with pendent side chains, ie. of general structure: ##STR2## Where(CH₂)m-X is the side chain and R is hydrogen or alkyl in the case ofpolyalkylacylates, being methyl in polymethacrylates.

DESCRIPTION OF THE INVENTION

According to the present invention there is provided a novel LCPmaterial based on fumarate and maleate all-esters having improved liquidcrystal properties over known LCP's, having a general formula I;##STR3## R₁ and R₂ may or may not be the same but have the followinggeneral structure: ##STR4## p=2 to 14; q=0 or 1;

r=1 or 2;

s=1 or 2;

X=O, CO₂, O₂ C, CH₂ ;

Y=C₂ H₄, O, CO₂, O₂ C;

Z=CN, halogen, R, CO₂ R, OR, O₂ CR, wherein R=chiral or achiral;

provided that when Z=alkoxy then q=0.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The general met,hod of preparation of LCP's of formula I is bypolymerisation of a compound of general structure:

    R.sub.l --O.sub.2 C--CH═CH--CO.sub.2 --R.sub.2

Wherein R₁ and R₂ have the general structure defined above.

EXAMPLE 1 ##STR5## Step 1

4-hydroxy-4'cyanobiphenyl was stirred at room temperature with11-bromo-1-undecanoic acid and trifluoroacetic acid in dichloromethanefor 24 hours. The product was purified by recrystallisation from IMS.

Step 2

The product from step 1 was stirred at room temperature with fumaricacid and sodium hydride in hexamethyl phosphoramide for 18 hours, Thesolution was acidified and separated in ether/water, The product waspurified by recrystallisation from IMS.

Step 3

The monomer was then stirred at 50°-80° C. in a little1,2-dichloroethane with azoisobutyronitrile as the initiator for 24hours. The polymer was separated by reprecipitation from DCM/IMS.

It will be appreciated that it is not intended to limit the invention tothe above example only, many variations, such as might readily occur toone skilled in the art, being possible, without departing from scopethereof as defined in the appended claims.

We claim:
 1. A liquid crystal polymer having the formula I: ##STR6##where n is the number of repeat units and R₁, and R₂ which may be thesame or different, have the structure: ##STR7## where A is independentlyselected from phenyl, fluorophenyl or cyclohexyl;p is 2 to 14, q is 0 or1, r is 1 or 2, s is 1 or 2, X is O, CO₂ or O₂ C or CH₂, and Y is C₂ H₄,O, CO₂ or O₂ C.
 2. A liquid crystal polymer of the formula ##STR8##wherein n is the number of repeat units in the polymer.
 3. A method ofsynthesis of a compound of the formula: ##STR9## where n is the numberof repeat units and R₁ and R₂, which may be the same or different, havethe structure: ##STR10## where A is independently selected from phenyl,fluorophenyl or cyclohexyl;p is 2 to 14, q is 0 or 1, r is 1 or 2, s is1 or 2, X is O, CO₂ or O₂ C CH₂, and Y is C₂ H₄, O, CO₂ or O₂ C saidprocess comprising polymerizing a compound of the formula

    R.sub.1 --O.sub.2 C--CH═CH--CO.sub.2 --R.sub.2

wherein R₁ and R₂, which may be the same or different, have thestructure given above.